RMAN Crosscheck and DELETE EXPIRED taking a long time for large catalog entries

For our larger databases with many 100's or 1000s of backup pieces the admin operations of RMAN are very slow when interacting with Netbackup. Are there tools on the netbackup side to diagnose this? We have verified with Oracle that RMAN catalog is not the issue. Its taking nearly 15minutes per delete backup piece operation. Any thoughts on this?

Is there an index or catalog operation for the media server catalogs that we should have the netbackup admins perform?

NetBackup for Oracle Agent designed to reduce the chance that an Oracle backup could not be found for restore, due to complexities that can be introduced by certain Recovery Manager (RMAN) procedures and conventions. Under normal circumstances, this allows an available backup to be found sooner than before these changes. If the backup has expired in the NetBackup catalog, however, significant additional checking is done before RMAN is informed that NetBackup is not able to locate the backup image. This results in longer execution time for RMAN "crosscheck" and "delete expired" operations.

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A better approach to manage the catalog synchronization is to use the Oracle and Symantec recommended method. This method is to set the backup retention as an RMAN attribute, rather than a NetBackup attribute, and having RMAN delete obsolete, but unexpired, backups from NetBackup